1. Field of the Invention
The present invention relates to an arteriosclerosis evaluating apparatus that evaluates arteriosclerosis of a living subject, based on a characteristic of subject's artery in a state in which difference of internal and external pressure of the artery is in equilibrium.
2. Related Art Statement
Evaluation of arteriosclerosis is frequently done for the purpose of, e.g., preventing adult disease such as cerebral hemorrhage or ischemic heart disease, and improvements of the evaluation technique are needed. There is known an arteriosclerosis evaluating apparatus that uses pulse-wave propagation velocity as an index for evaluating arteriosclerosis. This arteriosclerosis evaluating apparatus is disclosed by, e.g., Japanese Patent Publication No. 2001-190506. The disclosed arteriosclerosis evaluating apparatus includes a blood pressure measuring means for measuring a diastolic blood pressure of a living subject; a normal pulse-wave propagation velocity calculating means for calculating, on an assumption that the subject is normal, a normal pulse-wave propagation velocity of the subject, based on an actual age of the subject and the measured diastolic blood pressure of the subject, according to a predetermined formula; an actual pulse-wave propagation velocity calculating means for calculating an actual pulse-wave propagation velocity of the subject, based on an actual pulse wave detected from the subject; and an index calculating means for calculating, as an index of arteriosclerosis, a difference of the actual and normal pulse-wave propagation velocities. As arteriosclerosis of a living subject advances, an actual pulse-wave propagation velocity of the subject deviates from a normal pulse-wave propagation velocity of the same. Thus, the arteriosclerosis of the subject can be easily evaluated.
The above-indicated arteriosclerosis evaluating apparatus that uses the pulse-wave propagation velocity as the evaluation index has been so simplified in construction and so lowered in price, owing to the technical developments, that the apparatus can be actually used on living subjects. However, even now, the evaluating apparatus needs a considerably complex construction and accordingly has some limits to reduction of production cost.
In this background, the Inventors have performed extensive studies and researches for developing a technique of evaluating arteriosclerosis based on a new index that has never been used. One of the results obtained by the Inventors is such a finding that a relationship between difference of internal and external pressure of artery's wall of each individual subject in a state in which the difference is in equilibrium, and diameter of the artery, or a relationship between the difference of internal and external pressure of artery's wall and amplitude of pulse wave detected from the artery, is specific to the each individual subject. Based on this finding, the Inventors have developed a new arteriosclerosis evaluating apparatus.